Nap schedule for a catnapper?

My son is almost 5 months old and I want to get him on a schedule but I have yet to find one for babies who take really short naps (like 30ish minutes). I’ve tried lengthening his naps but nothing I’ve tried so far has worked. He’s soooo crabby all the time and I feel like I’m always putting him down too early so he cries for like half an hour and fights sleep or too late. I’m hoping I can get him to nap longer if I put him on a schedule but every schedule I’ve found assumed your baby naps 1.5-2 hours at a time so he ends up being awake too long before the next nap on the schedule. 😐